#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
const ll mod = 998244353;
namespace math{
	const ll N = 300005;
	ll fac[N+5],pw[N+5],inv[N+5];
	ll qpow(ll a,ll b){
		ll ans=1,base=a;
		while(b){
			if(b&1) ans=ans*base%mod;
			base=base*base%mod; b>>=1;
		}
		return ans;
	}
	void init(){
		fac[0]=inv[0]=pw[0]=1;
		for(ll i=1;i<=N;i++) fac[i]=fac[i-1]*i%mod,pw[i]=pw[i-1]*2%mod;
		inv[N]=qpow(fac[N],mod-2);
		for(ll i=N-1;i>=1;i--) inv[i]=inv[i+1]*(i+1)%mod;
	}
	inline ll binom(ll x,ll y){
		if(x<0 || y<0 || x<y) return 0;
		return fac[x]*inv[y]%mod*inv[x-y]%mod;
	}
	inline ll perm(ll x,ll y){
		if(x<0 || y<0 || x<y) return 0;
		return fac[x]*inv[x-y]%mod;
	}
}
ll ans;
using namespace math;
char s[300005];
ll fun(ll x,ll y,ll w){
	x=max(x, w); if(x>y) return 0;
	return (binom(y+1,w+1)-binom(x,w+1)+mod)%mod;
}
ll n;
void recalc(ll l,ll r){
//	cout<<"recalcing "<<l<<","<<r<<endl;
//	cout<<"ans = "<<ans<<endl;
	for(ll p=l-1;p<r;p++){
		ans=(ans-fun(n-r+p,n-1,p)+mod)%mod;
	}
//	cout<<"origin: "<<ans<<endl;
	ans=(ans+(r-l+1)*binom(l-1+n-r,n-r))%mod;
//	cout<<"all: "<<ans<<endl;
	if(l>1){
		for(ll i=l;i<r;i++){
			ans=(ans+(i-l+1)*binom(l-2+n-i,n-i))%mod;
		}
	}
	if(r<n){
		for(ll i=l+1;i<=r;i++){
			ans=(ans+(r-i+1)*binom(i-2+n-r,i-1))%mod;
		}
	}
//	cout<<"now: "<<ans<<endl;
}
int main(){
	init();
	scanf("%s", s+1);
	n=strlen(s+1);
	ans=pw[n]-1;
	
//	cout<<"first "<<ans<<endl;
	for(ll i=1;i<=n;){
		ll j=i;
		while(j<n && s[j+1]==s[i]) j++;
		recalc(i,j);
		i=j+1;
	}
	printf("%lld\n", ans);
	return 0;
}